mesa/src/glsl/glcpp
Kenneth Graunke 9142ade154 glcpp: Don't use infinite lookhead for #define differentiation.
Previously, we used lookahead patterns to differentiate:

   #define FOO(x)  function macro
   #define FOO (x) object macro

Unfortunately, our rule for function macros:

   {HASH}define{HSPACE}+/{IDENTIFIER}"("

relies on infinite lookahead, and apparently triggers a Flex bug where
the generated code overflows a state buffer (see YY_STATE_BUF_SIZE).

There's no need to use infinite lookahead.  We can simply change state,
match the identifier, and use a single character lookahead for the '('.
This apparently makes Flex not generate the giant state array, which
avoids the buffer overflow, and should be more efficient anyway.

Fixes piglit test 17000-consecutive-chars-identifier.frag.

NOTE: This is a candidate for every release branch ever.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Carl Worth <cworth@cworth.org>
2012-10-25 14:52:53 -07:00
..
tests glsl: glcpp: Extend testing of #line directives 2012-06-26 15:23:55 -07:00
.gitignore automake: convert libglsl 2012-07-13 12:43:41 +01:00
glcpp-lex.l glcpp: Don't use infinite lookhead for #define differentiation. 2012-10-25 14:52:53 -07:00
glcpp-parse.y glcpp: Don't use infinite lookhead for #define differentiation. 2012-10-25 14:52:53 -07:00
glcpp.c mesa/glsl: rename preprocess to glcpp_preprocess 2012-09-15 08:22:55 +10:00
glcpp.h mesa/glsl: rename preprocess to glcpp_preprocess 2012-09-15 08:22:55 +10:00
Makefile.am glcpp: fix abuse of yylex 2012-09-15 08:20:56 +10:00
pp.c mesa/glsl: rename preprocess to glcpp_preprocess 2012-09-15 08:22:55 +10:00
README Revert "glcpp: Demote "macro redefined" from an error to a warning" 2011-01-29 08:21:05 +10:00

glcpp -- GLSL "C" preprocessor

This is a simple preprocessor designed to provide the preprocessing
needs of the GLSL language. The requirements for this preprocessor are
specified in the GLSL 1.30 specification availble from:

http://www.opengl.org/registry/doc/GLSLangSpec.Full.1.30.10.pdf

This specification is not precise on some semantics, (for example,
#define and #if), defining these merely "as is standard for C++
preprocessors". To fill in these details, I've been using a draft of
the C99 standard as available from:

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

Any downstream compiler accepting output from glcpp should be prepared
to encounter and deal with the following preprocessor macros:

	#line
	#pragma
	#extension

All other macros will be handles according to the GLSL specification
and will not appear in the output.

Known limitations
-----------------
The __LINE__ and __FILE__ macros are not yet supported.

A file that ends with a function-like macro name as the last
non-whitespace token will result in a parse error, (where it should be
passed through as is).